Current mobile or computer devices use a variety of different navigation mechanisms. Some of these present a mousing surface for direct manipulation by a finger (or other part of the body), and work by producing images of the finger as it moves on the mousing surface, translating this finger movement to movement of a cursor (for example) on a screen. In this respect a navigation device of this type works in a similar fashion to an optical mouse, and is referred to as an optical navigation device.
It is often desirable to have an optical navigation device backlit. However, this can lead to performance degradation should the backlight remain on constantly. This means that the backlight illuminates the mousing surface and degrades the contrast of a fingerprint, thereby reducing the signal-noise ratio of the acquired image.